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APPLICATIONS OF XRD,DSC,DTA
Presented by
Dr. A. Suneetha
Dept. of Pharm. Analysis
Hindu College of Pharmacy
X-RAY DIFFRACTION
• When a beam of X-radiation is incident
upon a substance, interactions of radiation
with electrons of substance results in
scattering.
• X-rays scattered from a crystalline structure
constructively interferes and produces a
diffracted beam.
APPLICATIONS OF X-RAY
DIFFRACTION
1) Identification of crystals
2) Characterization of polymers
3) For particle size & shape analysis
e.g.Accurate determination of oxide nano particle
size & shape based on X-ray powder diffraction
4) State of anneal in metals
5) Differentiation of various phases
6) Miscellaneous
IDENTIFICATION OF CRYSTALS
• The analytical applications of XRD are numerous.
• The patterns obtained are characteristic of the particular compound crystals
• Eg., NaCl crystals(a) and KCl crystals(b) gives different diffraction patterns.(c) mixed
• By comparing with standard we can identify unknown crystalline compounds
CHARACTERISATION OF POLYMER
• Powder method can be used to
determine the degree of crystallinity
of the polymer.
• The non crystalline portion simply
scatters the X-ray beam to give
continuous background while the
crystalline portion causes diffraction
lines .
• The ratio of the area of the diffraction
peaks to the scattered radiation is
proportional to the ratio of
crystallinity and non crystalline
material,gives purity of the polymer.
STATE OF ANNEAL IN METALS
• A property of metals that can be determined by x-ray diffraction is the state of anneal.
• Well-annealed metals are in well-ordered crystal form and give sharp diffraction lines.
• If the metal is subjected to drilling ,hammering its crystals become broken and the x-ray pattern more diffuse.
Diffraction angle(2 )
Inte
nsi
ty→
90 1800
Crystal
90 1800
Inte
nsi
ty→ Liquid / Amorphous solid
90 1800
Diffraction angle (2) →
Inte
nsi
ty→
Mono atomic gas
SCHEMATIC DIFFERENCE BETWEEN
THE DIFFRACTION PATTERNS OF VARIOUS PHASES
Diffraction angle(2 )
MISCELLANEOUS
1)SOIL CLASSIFICATION
• Different types of soils such as clay,sandy etc., exhibit
different types and degrees of crystallinity.
• This gives information concerning soil structure.It also
tells us the mechanism of soil erosion.
2)Weathering and degradation of natural minerals.Based on
the results stable polymers have been developed.
3)Corrosion of products can be identified. So Metals and
alloys that are resistant to corrosion have been developed.
4)Identification of crystalline compounds that may originate in the body (eg.,gall stones)
5)Tooth enamel and dentine have been examined by XRD.This gives possible approaches to cure the tooth decay.
6)XRD is a major tool in elucidating the structure of RNA and DNA
ELECTRON MICROPROBE
• Nondestructive
• Determines composition
of tiny amounts of solids.
• Virtually all elements can
be analyzed.
An Electron Microprobe
ABSORPTIOMETRY
• Chemical analysis is possible for gases, lipids or
solids to measure densities ,porosities as well as
coating, plating and insulation thickness.
• Most often applied to patients in measurements
of bone densities, iodine in the thyroid gland,
liver diseases and other medical uses.
• Two types Single and Dual X-ray
Absorptiometry.
SINGLE X-RAY ABSORPTIOMETRY
• Single X-ray absorptiometry is used to measure
the bone mineral content.
• Used for diagnosis of osteoporosis.
• Provides reasonable accuracy and precision and
low radiation exposure.
DUAL X-RAY ABSORPTIOMETRY
• Used when single X-
ray absorptiometry is
not feasible.
• Used in areas with
variable soft tissue and
composition such as
the spine, hip or the
whole body.A dual x-ray absorptiometry
RADIOGRAPHY
• Involves use of registration on film, of the
differential absorption of a beam passing
through a specimen.
• Medical uses.
• Industrial uses.
• Nondestructive method.
DSC APPLICATIONS
• Liquid crystals
• Oxidative stability
• Estimate the degree of crystallinity
• General chemical analysis
• Food science
• Polymers
LIQUID CRYSTALS
DSC is used in the study of liquid crystals.
As some forms of matter go from solid to liquid they
go through a third state, which displays properties of
both phases.
This anisotropic liquid is known as a liquid crystalline
or mesomorphous state.
Using DSC, it is possible to observe the small energy
changes that occur ,as matter transitions from a solid
to a liquid crystal and from a liquid crystal to an
isotropic liquid.
OXIDATIVE STABILITY
Using differential scanning calorimetry , stability to
oxidation can be studied.
First, the sample is brought to the desired test temperature
under an inert atmosphere, usually nitrogen.
Then, oxygen is added to the system. Any oxidation that
occurs is observed as a deviation in the baseline.
Such analysis can be used to determine the stability and optimum storage conditions for a material or compound
ESTIMATE THE DEGREE OF CRYSTALLIZATION
DSC is used to monitor the isothermal crystallization of polyethylene.
From the given themogramthe area under the exothermic peak can be used to estimate the degree of crystallinity that has occur at this temperature.
At 124˚c,20 min are required for maximum crystallinity.
GENERAL CHEMICAL ANALYSIS
• Freezing-point depression can be used as a purity analysis
tool when analyzed by DSC
This is possible because the temperature range over which a
mixture of compounds melts is dependent on their relative
amounts
• Consequently, less pure compounds will exhibit a broadened
melting peak that begins at lower temperature than a pure compound.
POLYMERS
• DSC is used widely for examining polymers to check their
composition, Melting points and glass transition temperatures
• This method can show up possible polymer degradation by
the lowering of the expected melting point.
APPLICATIONS OF DTA
Characterization of polymers Identification of polymers Study of phase transitions Studying the thermal behavior of simple inorganic
species Determination of melting and boiling pointsMiscellaneous
CHARACTERISATION OF POLYMERS
DTA is a powerful and
widely used tool for
studying and
characterizing polymers.
The given thermogram
illustrates the type of
physical and chemical
changes in polymeric
materials
In the given differential
thermogram of a physical
mixture of seven commercial
polymers. Each peak
corresponds to the melting
point of one of the
components.
As melting point is
characteristic to each
polymer .
Clearly DTA has the potential
use of identifying polymers.
An important use of DTA is for the generation of phase diagrams and the study of phase transitions.
An example is shown in figure which is a differential thermogram of sulphur in which the peak at 113°C corresponds to the solid-phase change from rhombic to monoclinic form where as the peak at 124°C corresponds to M.P of the element.
Liquid sulphur is known to exist in atleast in three forms and the peak at 179°C apparently involves these transitions while the peak at 446°C corresponds to the B.P of sulphur.
DIFFERENTIAL THERMOGRAM OF SULPHUR
B.P
LIQUID
SOLID
M.P
STUDYING THE THERMAL BEHAVIOUR OF A SIMPLE INORGANIC SPECIES
DTA thermogram is obtained by heating calicium oxalate mofonohydrate in a flowing stream of air.
The two minima indicate that the sample became cooler than the reference material as a consequence of the two endothermic reactions that are shown by the equations below the minima.
The single maxima indicates that oxidation of calcium oxalate to give calcium carbonate and carbon dioxide is exothermic.
DTA provides a simple and accurate way of determining the melting, boiling and decomposition points of organic compounds.
The given thermogram for benzoic acid at atmospheric pressure(A) and at 200psi(B).
The first peak corresponds to the melting point and the second peak corresponds to the boiling point of the benzoic acid.
MISCELLANEOUS
DTA is of great importance in the fields of ceramics,minerology
and metallurgy.
Composition of mixed clays can be quickly identified.
Characterization of limestone used in Portland cement .
Thermograms of typical explosives and propellants provide
useful information regarding the manufacture, storage and
applications of these high energy materials.
REFERENCES
PRINCIPLES OF INSTRUMENTAL ANALYSIS ---
SKOOG. HOLLER. NEIMAN
INSTRUMENTAL METHODS OF CHEMICAL ANALYSIS ---
B.K. SHARMA
INSTRUMENTAL METHODS OF CHEMICAL ANALYSIS ---
GURDEEP R. CHATWAL, SHAM K. ANAND
INSTRUMENTAL METHODS OF ANALYSIS ---
WILLARD, MERRITT, DEAN, SETTLE
www.xraydiffrac.com/xrd.htm